Three dimensional simulation of fluid flow in X‐ray CT images of porous media     

A. Al‐Omari  E. Masad 《国际地质力学数值与分析法杂志》2004,28(13):1327-1360

A numerical scheme is developed in order to simulate fluid flow in three dimensional (3‐D) microstructures. The governing equations for steady incompressible flow are solved using the semi‐implicit method for pressure‐linked equations (SIMPLE) finite difference scheme within a non‐staggered grid system that represents the 3‐D microstructure. This system allows solving the governing equations using only one computational cell. The numerical scheme is verified through simulating fluid flow in idealized 3‐D microstructures with known closed form solutions for permeability. The numerical factors affecting the solution in terms of convergence and accuracy are also discussed. These factors include the resolution of the analysed microstructure and the truncation criterion. Fluid flow in 2‐D X‐ray computed tomography (CT) images of real porous media microstructure is also simulated using this numerical model. These real microstructures include field cores of asphalt mixes, laboratory linear kneading compactor (LKC) specimens, and laboratory Superpave gyratory compactor (SGC) specimens. The numerical results for the permeability of the real microstructures are compared with the results from closed form solutions. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

On the possibility of earth-type habitable planets around 47 UMa     

Manfred Cuntz  Werner von Bloh  Siegfried Franck 《Icarus》2003,162(1):214-221

We investigate whether Earth-type habitable planets can in principle exist in the planetary system of 47 UMa. The system of 47 UMa consists of two Jupiter-size planets beyond the outer edge of the stellar habitable zone, and thus resembles our own Solar System most closely compared to all exosolar planetary systems discovered so far. Our study of habitability deliberately follows an Earth-based view according to the concept of Franck and colleagues, which assumes the long-term possibility of photosynthetic biomass production under geodynamic conditions. Consequently, a broad variety of climatological, biogeochemical, and geodynamical processes involved in the generation of photosynthesis-driven life conditions is taken into account. The stellar luminosity and the age of the star/planet system are of fundamental importance for planetary habitability. Our study considers different types of planetary continental growth models and takes into account a careful assessment of the stellar parameters. In the event of successful formation and orbital stability, two subjects of intense research, we find that Earth-type habitable planets around 47 UMa are in principle possible! The likelihood of those planets is increased if assumed that 47 UMa is relatively young (?6 Gyr) and has a relatively small stellar luminosity as permitted by the observational range of those parameters.  相似文献   

A simple model for lensing by black holes in galactic nuclei     

M. C. Werner  N. W. Evans 《Monthly notices of the Royal Astronomical Society》2006,368(3):1362-1368

The lensing properties of the Plummer model with a central point mass and external shear are derived, including the image multiplicities, critical curves and caustics. This provides a simple model for a flattened galaxy with a central supermassive black hole. For the Plummer model with black hole, the maximum number of images is four, provided the black hole mass is less than an upper bound which is calculated analytically. This introduces a method to constrain black hole masses by counting images, thus applicable at cosmological distance. With shear, the maximum number of images is six and we illustrate the occurrence of an astroid caustic and two metamorphoses.  相似文献   

The accessibility of a network: The great lakes corridor passenger as an example     

Dr. Abdullah R. Al.-Kandari 《GeoJournal》1986,12(3):255-266

  相似文献   

On the properties of the local interstellar medium     

Al. A. Suchkov 《Astrophysics》1985,23(1):452-458

  相似文献   

The global Frasnian-Famennian »Kellwasser Event«   总被引：5，自引：0，他引：5  

Werner Buggisch 《International Journal of Earth Sciences》1991,80(1):49-72

During the UppermostP. gigas conodont zone (P. linguiformis zone) the stepwise Frasnian extinction culminates in the global transgressive-regressive Frasnian-Famennian »Kellwasser event«. Most pelagic organisms of the tropical marine environment are more or less affected by this mass extinction. During the early Upper Devonian extinction rates are clearly related to the deposition of black shales and the storage of a great amount of organic carbon in the (shelf) sediments. Contemporaneous positive excursions of the ¹³C recorded from pelagic limestones of Europe and Australia prove a worldwide change in the CO₂ content of the oceans surface water which is in balance with the atmosphere. If the climate is controlled by the CO₂ content of the atmosphere, a cyclic operation process might have developed with the succession: transgression — high organic production — deposition of organic carbon — lowering of CO₂ in the atmosphere — icehouse effect — polar glaciation — regression — erosion of organic carbon and re-supply of CO₂ to the ocean and atmosphere — greenhouse effect — deglaciation — transgression. During the change from a greenhouse to an icehouse effect an overturn of the anoxic oceans probably was one of the causes for the mass killing of low latitude marine organisms.

---

Zusammenfassung Während der OberstenP. gigas-Zone (=P. linguiformis-Zone) kulminiert das stufenweise Erlöschen der Frasne Organismen im globalen transgressiv-regressiven »Kellwasser-Ereignis«, das die Frasne-Famenne-Grenze markiert. Die meisten Organismengruppen der tropischen Meere werden mehr oder weniger von dem Massensterben betroffen. Während des tiefen Oberdevons sind die Aussterberaten offensichtlich mit der Ablagerung von Schwarzschiefern verknüpft, in denen eine große Menge organischen Kohlenstoffs auf den Schelfen fixiert wird. Gleichzeitige positive Exkursionen der ¹³C-Kurven, die in pelagischen Kalken aus Europa und Australien gemessen wurden, deuten auf eine weltweite Änderung der CO₂-Gehalte des ozeanischen Oberflächenwassers und der Atmosphäre hin.Sollte das Klima vom CO₂ in der Atmosphäre gesteuert werden, könnte sich folgender Autozyklus entwickelt haben: Transgression — hohe organische Produktion — Ablagerung von organischem Kohlenstoff — Erniedrigung des CO₂-Gehaltes in der Atmosphäre — Abkühlung — polare Vereisung-Regression — Erosion und Oxidation von organischem Kohlenstoff — Erhöhung des CO₂-Gehaltes in der Atmosphäre — Treibhauseffekt — Abschmelzen der polaren Vereisung — Transgression. Aufsteigende anoxische Wässer beim Übergang vom Treibhaus- zum »Kühlhauseffekt« dürften eine der Ursachen für das Massensterben tropischer mariner Organismen gewesen sein.

---

Résumé Au cours de la partie supérieure de la zone de conodontes àP. gigas (= zone àP. linguiformis), l'extinction progressive des organismes frasniens a culminé au moment de l'événement de Kellwasser, marqué par une transgression-régression globale à la limite Frasnien-Famennien. La plupart des organismes pélagiques des milieux marins tropicaux ont été affectés à des degrés divers par cette extinction de masse. Pendant le début du Dévonien supérieur, les taux d'extinction sont clairement en relation avec le dépôt de boues noires et le stockage d'une grande quantité de matière organique dans les sédiments de shelf. Simultanément, des variations positives de ¹³C enregistrées dans des calcaires pélagiques d'Europe et d'Australie indiquent un changement modial de la teneur en CO₂ de l'eau de surface des océans et de l'atmosphère.Si on admet que le climat est régi par la teneur en CO₂ de l'atmosphère, le processus cyclique suivant a pu se développer: transgression — forte production organique — dépôt de carbone organique — baisse de la teneur en CO₂ de l'atmosphère — refroidissement — glaciation polaire — régression — érosion et oxydation du carbone organique — élévation de la teneur en CO₂ de l'atmosphère — effet de serre — fusion des glaces polaires — transgression. Lors du passage du stade de l'effet de serre à celui du refroidissement, une remontée des eaux anoxiques océaniques peut être à l'origine de l'extinction de masse des organismes marins tropicaux.

---

, , P. gigas, - Kellwasser, . . , . ¹³ , , ₂ , . ₂ , : — — _opr.- ₂ — — — — — ₂ — - — . » « .

  相似文献   

Geomorphic changes in Ras Al-Subiyah area,Kuwait     

A. Al Hurban  H. El-Gamily  A. El-Sammak 《Environmental Geology》2008,54(7):1377-1390

The Ras Al-Subiyah area is considered one of the most promising areas in Kuwait for future development. This development will include a new town called Subiyah and its associated infrastructure. This area is also being considered as the location for connection between Boubyan Island, which is now undergoing major development and the Kuwait mainland. The present study investigates the geomorphology of the Ras Al-Sabiyah area in the northern sector of Kuwait. The study area is generally flat, and it is located west of the Jal Az-Zor escarpment. It is bordered on the east by the Khor Al-Sabiyah tidal channel and on the south by Kuwait Bay. The area receives sediments from several sources; currently the most important are aeolian sediments and the deposition of mud delivered through the Khor Al-Sabiyah from the Iraqi marshes. The study area has been subjected to severe environmental changes due to the Gulf wars and the drainage of Iraqi marshes and the associated artificial changes in fluvial system. Twenty-two surface sediments were collected from the Ras Al-Subiyah area. Samples were collected to include the main geomorphologic characteristic features of the study area. Field observations and remote sensing images from 1990 and 2001 were used to produce an updated geomorphologic map for the Ras Al-Subiyah and a map showing geomorphic changes between 1990 and 2001. Grain size of the surface sediment ranges from gravel to medium sand. In general, grain size statistical analysis indicates that most of the areas are composed of two or more classes of sands transported and deposited from different sources including aeolian, sabkhas, river and the bays. The variability in the grain size statistical parameters may be attributed to the complexity of surface morphology as well as the diversity in the type of depositional environment in the Ras Al-Subiyah area. The total area subjected to change during the 12-year period (1990–2001) is about 32 km² as calculated using GIS techniques.  相似文献   

Determination of fluid/melt partition coefficients by LA-ICPMS analysis of co-existing fluid and silicate melt inclusions: Controls on element partitioning   总被引：8，自引：0，他引：8  

Zoltán Zajacz  Werner E. Halter  Marcel Guillong 《Geochimica et cosmochimica acta》2008,72(8):2169-2197

Analyses of co-existing silicate melt and fluid inclusions, entrapped in quartz crystals in volatile saturated magmatic systems, allowed direct quantitative determination of fluid/melt partition coefficients. Investigations of various granitic systems (peralkaline to peraluminous in composition, log fO₂ = NNO−1.7 to NNO+4.5) exsolving fluids with various chlorinities (1-14 mol/kg) allowed us to assess the effect of these variables on the fluid/melt partition coefficients (D). Partition coefficients for Pb, Zn, Ag and Fe show a nearly linear increase with the chlorinity of these fluid (D_Pb ∼ 6 ∗ m_Cl, D_Zn ∼ 8 ∗ m_Cl, D_Ag ∼ 4 ∗ m_Cl, D_Fe ∼ 1.4 ∗ m_Cl, where m_Cl is the molinity of Cl). This suggests that these metals are dissolved primarily as Cl-complexes and neither oxygen fugacity nor the composition of the melt affects significantly their fluid/melt partitioning. By contrast, partition coefficients for Mo, B, As, Sb and Bi are highest in low salinity (1-2 mol/kg Cl) fluids with maximum values of D_Mo ∼ 20, D_B ∼ 15, D_As ∼ 13, D_Sb ∼ 8, D_Bi ∼ 15 indicating dissolution as non-chloride (e.g., hydroxy) complexes. Fluid/melt partition coefficients of copper are highly variable, but highest between vapor like fluids and silicate melt (D_Cu ? 2700), indicating an important role for ligands other than Cl. Partition coefficients for W generally increase with increasing chlorinity, but are exceptionally low in some of the studied brines which may indicate an effect of other parameters. Fluid/melt partition coefficients of Sn show a high variability but likely increase with the chlorinity of the fluid (D_Sn = 0.3-42, D_W = 0.8-60), and decrease with decreasing oxygen fugacity or melt peraluminosity.  相似文献   

Differential-Thermo-Analysen von einigen Karbonat-Mineralen     

Werner Smykatz-Kloss 《Contributions to Mineralogy and Petrology》1964,9(5):481-502

  相似文献   

Environmental overview of Eckernförde Bay,northern Germany     

T. H. Orsi  F. Werner  D. Milkert  A. L. Anderson  W. R. Bryant 《Geo-Marine Letters》1996,16(3):140-147

This environmental overview of Eckernförde Bay (northern Germany) summarizes the results of previous studies relevant to the Office of Naval Research's Coastal Benthic Boundary Layer (CBBL) Baltic field exercise conducted during 1993–1994. Significant environmental characteristics include the following: (1) surface sediment distribution is related to water depth, dictated primarily by hydrodynamic reworking of older glacial deposits; (2) the origin and characteristics of small-scale sedimentary structures depend on storm-generated waves and currents; (3) the proximity of the sea surface and sediment —water interface results in a pelagic—benthic coupling that drives biogeochemical processes and produces organicrich, acoustically turbid sediments; and (4) the bay floor is complicated topographically by pockmarks and manmade sedimentary structures.  相似文献